A system for storing and purging fuel vapors from a canister is described in U.S. Patent Application 2007/0227515. The patent application describes a method for using the output of a compressor to provide a positive pressure to a fuel vapor storage canister. The positive pressure is used to move fuel vapors to the compressor's inlet and the canister is purged of fuel vapor.
The above-mentioned system can also have disadvantages. For example, the system uses output from the compressor to purge fuel vapors from a canister, and the canister vapors are directed to the compressor inlet. Thus, air entering the canister during canister purge already contains fuel, thereby lowering purging efficiency.
The inventors herein have recognized the above-mentioned disadvantages and have developed a system and method that offers substantial improvements.